AMOLF, Science Park 104, 1098 XG Amsterdam, Netherlands.
Phys Rev Lett. 2020 Aug 14;125(7):078101. doi: 10.1103/PhysRevLett.125.078101.
The friction between cytoskeletal filaments is of central importance for the formation of cellular structures such as the mitotic spindle and the cytokinetic ring. This friction is caused by passive cross-linkers, yet the underlying mechanism and the dependence on cross-linker density are poorly understood. Here, we use theory and computer simulations to study the friction between two filaments that are cross-linked by passive proteins, which can hop between discrete binding sites while physically excluding each other. The simulations reveal that filaments move via rare discrete jumps, which are associated with free-energy barrier crossings. We identify the reaction coordinate that governs the relative microtubule movement and derive an exact analytical expression for the free-energy barrier and the friction coefficient. Our analysis not only elucidates the molecular mechanism underlying cross-linker-induced filament friction, but also predicts that the friction coefficient scales superexponentially with the density of cross-linkers.
细胞骨架丝之间的摩擦对于细胞结构的形成至关重要，例如有丝分裂纺锤体和胞质分裂环。这种摩擦是由被动交联剂引起的，但对于其潜在机制和对交联剂密度的依赖性了解甚少。在这里，我们使用理论和计算机模拟来研究由被动蛋白交联的两条细丝之间的摩擦，这些蛋白可以在物理上相互排斥的同时在离散的结合位点之间跳跃。模拟表明，细丝通过罕见的离散跳跃移动，这些跳跃与自由能势垒的穿越有关。我们确定了控制相对微管运动的反应坐标，并推导出了自由能势垒和摩擦系数的精确解析表达式。我们的分析不仅阐明了交联剂诱导的细丝摩擦的分子机制，还预测摩擦系数与交联剂密度呈超指数级增长。
